<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
			//非严格模式
			function testl(a){
				arguments[0] = 34;
				console.log(a);
			}
			//严格模式
			function test2(a){
				"use strict";
				arguments[0] = 34;
				console.log(a);
			}
			
			function test3(a,b = 10){
				'use strict'; //会报错
			};
			
			testl (20);
			test2(20);
			test3(5);
			
		</script>
	</body>
</html>
